(a) Field of the Invention
The present invention relates to filters for cigarettes. In one respect it relates to an air ventilated filter. In another respect, the invention relates to a cigarette filter having a plurality of longitudinally extending air-smoke channels formed herein.
(b) Description of the Prior Art
It is well known in the art of cigarette filters to utilize ambient air for the dilution of cigarette smoke prior to entering the smoker's mouth. The dilution of the smoke stream reduces the concentration of smoke particulates as well as gas phase components which are delivered to the mouth of the smoker. A number of means have been proposed and are utilized for introducing ventilating air into the cigarette. For example, the wrapper for the tobacco column may be made of a porous material which allows for introduction of air along the entire length of the cigarette thereby mixing and diluting the smoke stream as it passes therethrough. Also, the cigarette wrapper may be perforated at selected locations along the length of the cigarette to provide ports through which ventilating air enters the cigarette. Even further, it is known to perforate the wrapper of a filter at the end of the cigarette to allow for ventilating air to enter the filter for dilution of the smoke stream in the filter. Examples are shown in U.S. Pat. No. 3,860,011 and U.S. Pat. No. 4,174,719. It has also been proposed to make cigarette filters wherein the ventilating air and the smoke stream pass through the filter in separate streams and do not mix until they exit the filter. Examples of this type of filter are shown in U.S. Pat. No. 3,324,862; U.S. Pat. No. 3,390,684; U.S. Pat. No. 4,023,576 and U.S. Pat. No. 4,256,122. Still further it has been suggested, for example, in U.S. Pat. No. 3,756,250, to fabricate a ventilated cigarette filter with a void at the upstream end of the filter which functions as an air-smoke mixing chamber. Even further, U.S. Pat. No. 4,135,523 shows a ventilated cigarette filter formed with a spiral groove formed in the periphery of the filter wherein air and smoke are mixed together.